@[caojiaming](/user/775551) 一个集合的子集一共有 $2^n$ 个，其中 $n$ 是元素的个数
by xiaomimxl @ 2022-12-20 18:17:32
@[caojiaming](/user/775551)
`while` 了解一下
by tbdsh @ 2022-12-20 18:17:55
题目没告诉n
我不知道要读入多少个数
by caojiaming @ 2022-12-20 18:18:26
```cpp
int a;
while (cin >> a) {
//...
}
```
by Jasper08 @ 2022-12-20 18:19:39
@[caojiaming](/user/775551) `while(cin>>x)`
`x` 可替换为您需要获取的数据
by AZN_0975 @ 2022-12-20 18:20:13
谢了
但是自测如何结束
@[Jasper08](/user/581830)
by caojiaming @ 2022-12-20 18:21:13
如果要输入数组，可以这样：
```
for (i = 1; cin >> a[i]; i++);
```
$a$ 数组可以随意替换
by tbdsh @ 2022-12-20 18:21:19
@[caojiaming](/user/775551)
自测输入 `Ctrl + Z` 即可
by tbdsh @ 2022-12-20 18:21:42
@[caojiaming](/user/775551) 用 `Ctrl+Z`
by Jasper08 @ 2022-12-20 18:21:52
我这搞得只有20分
```cpp
#include <bits/stdc++.h>
using namespace std;
int a[31];
int main()
{
long long sum=0;
int i;
for(i=0;cin>>a[++i];)
{
sum+=a[i];
}
cout<<(long long)(pow(2,i-1)*sum);
return 0;
}
```
by caojiaming @ 2022-12-20 18:25:38